Intra-frame prediction and decoding methods and apparatuses for image signal

ABSTRACT

An intra-frame decoding method is provided. The method includes: obtaining, from a video code stream, prediction mode information of a first signal component of a current block; determining a prediction mode of the first signal component of the current block from a prediction mode set of the first signal component of the current block according to the prediction mode information of the first signal component of the current block, where the prediction mode set of the first signal component of the current block includes at least one of a linear model above (LMA) mode and a linear model left (LML) mode; obtaining a predicted value of a first signal component sampling point of the current block; and obtaining a reconstructed value of the first signal component sampling point of the current block according to the predicted value of the first signal component sampling point of the current block.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2012/084079, filed on Nov. 5, 2012, which claims priority toChinese Patent Application No. 201110347750.2, filed on Nov. 4, 2011,both of which are hereby incorporated by reference in their entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

TECHNICAL FIELD

The present invention relates to the field of communicationstechnologies, and in particular, to an intra-frame decoding method andapparatus for a signal component sampling point of an image block and aprediction method and apparatus for a signal component sampling point ofan image block.

BACKGROUND

Existing video image coding technologies include an intra-frame codingtechnology and an inter-frame coding technology. Intra-frame coding is atechnology of coding image content by using only spatial correlation ina currently coded image block. Inter-frame coding is a technology ofcoding a currently coded image block by using time correlation betweenthe currently coded image block and a coded image block.

To increase intra-frame coding efficiency for an image, an intra-frameprediction technology is first introduced in the H.264 Advanced VideoCoding (H.264/AVC) standard to remove spatial information redundancybetween a currently coded image block (hereinafter referred to as acurrent block) and an adjacent coded image block. The High EfficiencyVideo Coding (HEVC) solution is a new-generation video codingstandardization solution currently being studied by the InternationalOrganization for Standardization, which inherits and is extended fromthe intra-frame prediction coding technology in the H.264/AVC standard.A prediction mode set of a chrominance component of an image block mayinclude six optional prediction modes: a direct mode (DM) mode:prediction is performed by using a prediction mode of a luminancecomponent of a current block as a prediction mode of a chrominancecomponent of the current block; a linear method (LM) mode: a predictedvalue of a chrominance component sampling point is calculated based on acorrelation model by using a reconstructed value of a luminancecomponent sampling point, where a parameter of the correlation model isobtained through calculation according to reconstructed values ofluminance component and chrominance component sampling points rightabove and on the left of a current block; a direct current (DC) mode: anaverage value of reconstructed values of adjacent chrominance componentsampling points right above and on the left of a current block is usedas a predicted value of a chrominance component sampling point of thecurrent block; a planar mode: a predicted value of a chrominancecomponent sampling point of a current block is calculated based on anassumption of spatial smooth linear variation of values of chrominancecomponent sampling points; a horizontal mode: a reconstructed value of achrominance component sampling point on the left side of a current blockis used as a predicted value of all chrominance component samplingpoints in a same row of the current block; and a vertical mode: areconstructed value of an adjacent chrominance component sampling pointright above a current block is used as a predicted value of allchrominance component sampling points in a same column of the currentblock.

Among the foregoing prediction modes, the DC mode, the vertical mode,the horizontal mode, and the planar mode have a same basic principle ascorresponding prediction modes in the H.264/AVC standard, but specificimplementation methods are different. The LM mode and the DM mode aretwo newly added prediction modes.

However, in the existing HEVC solution, a prediction mode set of achrominance component cannot adapt to the diversity of edge positions ofa current block, and in some cases, a prediction effect needs to beimproved.

SUMMARY

Embodiments of the present invention provide an intra-frame decodingmethod and apparatus for a signal component sampling point of an imageblock and a prediction method and apparatus for a signal componentsampling point of an image block, so as to improve the accuracy ofintra-frame prediction of a current block.

An embodiment of the present invention provides a prediction method fora signal component sampling point of an image block, which includes:calculating, based on a correlation model, a predicted value of a firstsignal component sampling point of a current block according to areconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point above the current block and a reconstructed value of asecond adjacent signal component sampling point above the current block.

An embodiment of the present invention further provides a predictionmethod for a signal component sampling point of an image block, whichincludes: calculating, based on a correlation model, a predicted valueof a first signal component sampling point of a current block accordingto a reconstructed value of a second signal component sampling point ofthe current block and a parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point on the left side of the current block and a reconstructedvalue of a second adjacent signal component sampling point on the leftside of the current block.

An embodiment of the present invention further provides an intra-framedecoding method for a signal component sampling point of an image block,which includes: obtaining, from a video code stream, prediction modeinformation of a first signal component of a current block; determininga prediction mode of the first signal component of the current blockfrom a prediction mode set of the first signal component of the currentblock according to the prediction mode information of the first signalcomponent of the current block, where the prediction mode set of thefirst signal component of the current block includes at least one of alinear model above (LMA) mode and a linear model left (LML) mode;obtaining a predicted value of a first signal component sampling pointof the current block according to the prediction mode of the firstsignal component of the current block; and obtaining a reconstructedvalue of the first signal component sampling point of the current blockaccording to the predicted value of the first signal component samplingpoint of the current block.

An embodiment of the present invention further provides an intra-framedecoding method for a signal component sampling point of an image block,which includes: obtaining, from a video code stream, prediction modeinformation of a first signal component of a current block; determininga prediction mode of the first signal component of the current blockfrom a prediction mode set of the first signal component of the currentblock according to the prediction mode information of the first signalcomponent of the current block, where the prediction mode set of thefirst signal component includes a prediction mode based on a correlationmodel, and the prediction mode based on the correlation model isdetermined depending on a prediction mode of a second signal componentof the current block; obtaining a predicted value of a first signalcomponent sampling point of the current block according to theprediction mode of the first signal component of the current block; andobtaining a reconstructed value of the first signal component samplingpoint of the current block according to the predicted value of the firstsignal component sampling point of the current block.

An embodiment of the present invention further provides a predictionapparatus for a signal component sampling point of an image block, whichincludes: a first parameter unit configured to obtain a parameter of acorrelation model through calculation according to a reconstructed valueof a first adjacent signal component sampling point above a currentblock and a reconstructed value of a second adjacent signal componentsampling point above the current block; and a first predicting unitconfigured to calculate, based on the correlation model, a predictedvalue of a first signal component sampling point of the current blockaccording to a reconstructed value of a second signal component samplingpoint of the current block and the parameter of the correlation model.

An embodiment of the present invention further provides a predictionapparatus for a signal component sampling point of an image block, whichincludes: a second parameter unit configured to obtain a parameter of acorrelation model through calculation according to a reconstructed valueof a first adjacent signal component sampling point on the left side ofa current block and a reconstructed value of a second adjacent signalcomponent sampling point on the left side of the current block; and asecond predicting unit configured to calculate, based on the correlationmodel, a predicted value of a first signal component sampling point ofthe current block according to a reconstructed value of a second signalcomponent sampling point of the current block and the parameter of thecorrelation model.

An embodiment of the present invention further provides an intra-framedecoding apparatus for a signal component sampling point of an imageblock, which includes: a first obtaining unit configured to obtain, froma video code stream, prediction mode information of a first signalcomponent of a current block; a first determining unit configured todetermine a prediction mode of the first signal component of the currentblock from a prediction mode set of the first signal component of thecurrent block according to the prediction mode information of the firstsignal component of the current block, where the prediction mode set ofthe first signal component of the current block includes at least one ofan LMA mode and an LML mode; a third predicting unit configured toobtain a predicted value of a first signal component sampling point ofthe current block according to the prediction mode of the first signalcomponent of the current block; and a first calculating unit configuredto obtain a reconstructed value of the first signal component samplingpoint of the current block according to the predicted value of the firstsignal component sampling point of the current block.

An embodiment of the present invention further provides an intra-framedecoding apparatus for a signal component sampling point of an imageblock, which includes: a second obtaining unit configured to obtain,from a video code stream, prediction mode information of a first signalcomponent of a current block; a second determining unit configured todetermine a prediction mode of the first signal component of the currentblock from a prediction mode set of the first signal component of thecurrent block according to the prediction mode information of the firstsignal component of the current block, where the prediction mode set ofthe first signal component includes a prediction mode based on acorrelation model, and the prediction mode based on the correlationmodel is determined depending on a prediction mode of a second signalcomponent of the current block; a fourth predicting unit configured toobtain a predicted value of a first signal component sampling point ofthe current block according to the prediction mode of the first signalcomponent of the current block; and a second calculating unit configuredto obtain a reconstructed value of the first signal component samplingpoint of the current block according to the predicted value of the firstsignal component sampling point of the current block.

According to the technical solutions provided in the embodiments of thepresent invention, by using a technical means of introducing an LMA modeand an LML mode in a process of intra-frame prediction of a currentblock, the accuracy of intra-frame prediction of the current block isimproved.

BRIEF DESCRIPTION OF THE DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention more clearly, the following briefly introduces theaccompanying drawings required for describing the embodiments. Theaccompanying drawings in the following description show merely someembodiments of the present invention, and persons of ordinary skill inthe art may still derive other drawings from these accompanying drawingswithout creative efforts.

FIGS. 1A, 1B, and 1C are schematic diagrams of a luminance-chrominance(YUV) format;

FIG. 2 is a schematic diagram of an L-type template used for an LM mode;

FIGS. 3A and 3B are schematic diagrams showing distribution of samplingpoints in an L-type template and objects in a current block;

FIG. 4 is a schematic diagram of a template used for an LMA mode;

FIG. 5 is a schematic diagram of a template used for an LML mode;

FIG. 6 is a flowchart of an intra-frame decoding method for a signalcomponent sampling point of an image block according to an embodiment ofthe present invention;

FIG. 7 is a flowchart of an intra-frame decoding method for a signalcomponent sampling point of an image block according to anotherembodiment of the present invention;

FIG. 8 is an effect diagram of a V component of a reconstructed imageobtained by using an embodiment of the present invention;

FIG. 9 is an effect diagram of a V component of a reconstructed imageobtained by using the HEVC technical solution;

FIG. 10 is an effect diagram of a technical solution according to anembodiment of the present invention;

FIG. 11 is a schematic diagram of a prediction apparatus for a signalcomponent sampling point of an image block according to an embodiment ofthe present invention;

FIG. 12 is a schematic diagram of a prediction apparatus for a signalcomponent sampling point of an image block according to anotherembodiment of the present invention;

FIG. 13 is a schematic diagram of an intra-frame decoding apparatus fora signal component sampling point of an image block according to anembodiment of the present invention; and

FIG. 14 is a schematic diagram of an intra-frame decoding apparatus fora signal component sampling point of an image block according to anotherembodiment of the present invention.

DETAILED DESCRIPTION

The following clearly describes the technical solutions in theembodiments of the present invention with reference to the accompanyingdrawings in the embodiments of the present invention. The embodiments tobe described are merely a part rather than all of the embodiments of thepresent invention. All other embodiments obtained by persons of ordinaryskill in the art based on the embodiments of the present inventionwithout creative efforts shall fall within the protection scope of thepresent invention.

A video image signal generally includes one luminance component and twochrominance components. The luminance component is generally indicatedby a symbol Y, and the chrominance components are generally indicated bysymbols U and V. As shown in FIGS. 1A, 1B, and 1C, common YUV formatsinclude the following formats, where a cross shown in FIGS. 1A, 1B, 1Cindicates a luminance component sampling point, and a circle indicateseach chrominance component sampling point: a 4:4:4 format: indicatingthat no downsampling is performed on a chrominance component; a 4:2:2format: indicating that 2:1 horizontal downsampling is performed on achrominance component relative to a luminance component, but no verticaldownsampling is performed, where for every two U sampling points or Vsampling points, each scan line includes four Y sampling points; and a4:2:0 format: indicating that 2:1 horizontal downsampling and 2:1vertical downsampling are performed on a chrominance component relativeto a luminance component.

In a case where a video image uses a YUV4:2:0 format, if a luminancecomponent of an image block is an image block with a size of 2N×2N, achrominance component of the image block is an image block with a sizeof N×N. In the embodiments of the present invention, the technicalsolutions of the present invention are described by using the 4:2:0format as an example. However, it may be understood that, in addition tothe YUV4:2:0 format, the technical solutions of the present inventionmay also be applied to other YUV formats, or mutual prediction betweendifferent components in other video image formats, such as a red greenblue (RGB) format. In another aspect, a current block may be a squareblock, or may be a non-square rectangular block or an area in anothershape, to which the technical solutions provided in the embodiments ofthe present invention are also applicable.

For convenience of description, in the embodiments of the presentinvention, expressions such as a first signal component and a secondsignal component are used. If an image signal includes a luminancesignal component and a chrominance signal component, the first signalcomponent may be a chrominance component, and the second signalcomponent may be a luminance component; if the image signal includesthree signal components red (R), green (G), and blue (B), the firstsignal component may be any signal component in the three signalcomponents R, G, and B, and the second signal component may be a signalcomponent different from the first signal component in the three signalcomponents R, G, and B; and if the image signal is decomposed into aplurality of signal components in another manner, the first signalcomponent and the second signal component may be specified by using asimilar method.

In the embodiments of the present invention, because two chrominancecomponents can be predicted from a luminance component by using a samemethod, the technical solutions according to the embodiments of thepresent invention may be described in the following by using L toindicate a luminance component and using C to indicate any one ofchrominance components. A predicted value of any chrominance componentsampling point may be obtained by mapping a reconstructed value of aluminance component sampling point at a same position according to acorrelation function relation ƒ(x). When there is no luminance componentsampling point at the same position corresponding to a chrominancecomponent sampling point (a position relation between a luminancecomponent sampling point and a chrominance component sampling point inthe YUV 4:2:0 format as shown in FIG. 1C), a luminance component may befirst re-sampled to a position of the chrominance component samplingpoint to obtain L′, and then prediction is performed, as shown inFormula (2.1). In this case, each chrominance component sampling pointhas one luminance component value and one chrominance component value.Sample_(C) ^(pred) [j,i]=ƒ(Sample_(L) ′[j,i])  (2.1)

Herein, the correlation function relationship ƒ(x) is used to express acorrelation model from a luminance component value to a chrominancecomponent value of a sampling point, and it may be a linear function, ormay be another function such as a quadratic polynomial. The embodimentsof the present invention are described by using a linear function modelshown in Formula (2.2) as an example. Parameters α and β of the linearmodel may be obtained through calculation according to reconstructedvalues of a group of luminance component sampling points and chrominancecomponent sampling points.ƒ(x)=αx+β(2.2)

The group of selected sampling points used for calculating theparameters α and β is called a template in the embodiments of thepresent invention. In the embodiments of the present invention, as shownin FIG. 2, an L-type template is used for an LM mode. The LM mode is aprediction mode for calculating a predicted value of a first componentsampling point of a current block based on reconstructed values of firstadjacent signal component sampling points above and on the left side ofthe current block, reconstructed values of second adjacent signalcomponent sampling points above and on the left side of the currentblock, and a reconstructed value of a second component sampling point ofthe current block.

The accuracy of the parameters α and β directly influences the accuracyof the predicted value of the chrominance component sampling point. TheL-type template used for the foregoing LM mode includes only N adjacentpoints right above the current block and N adjacent points on the leftside of the current block. Generally, the L-type template is effective.For example, an image block shown in FIG. 3A includes two objects, whichhave different chrominance components (a grey area and a white arearepresent two objects). However, in the L-type template, a plurality ofsampling points belongs to a same object as a part of sampling points inthe current block. In this case, correlation between a luminancecomponent and a chrominance component derived from the sampling pointsin the L-type template is quite similar to correlation betweencomponents in the current block. Therefore, a value of a chrominancecomponent sampling point in the current block can be accuratelypredicted, based on the foregoing linear relation, from a reconstructedvalue of a luminance component sampling point. However, if the twoobjects in the current block are distributed as shown in FIG. 3B (a greyarea and a white area represent two objects with different chrominancecomponents), that is, no sampling point in the L-type template belongsto a same object as a sampling point in the grey area, in this case, theparameters α and β obtained through calculation cannot indicatecorrelation between a luminance component and a chrominance component ofthe grey area. As a result, a value of a chrominance component samplingpoint of the grey area cannot be accurately predicted by using a linearrelation derived in this case.

To accurately predict a value of a chrominance component sampling pointin a current block, the embodiments of the present invention provide twonew prediction modes, that is, an LMA mode and an LML mode.

As shown in FIG. 4, the LMA mode is a prediction mode for calculating apredicted value of a first component sampling point of a current blockbased on a reconstructed value of a first adjacent signal componentsampling point above the current block, a reconstructed value of asecond adjacent signal component sampling point above the current block,and a reconstructed value of a second component sampling point of thecurrent block.

In the embodiment of the present invention, the calculating thepredicted value of the first component sampling point of the currentblock based on the reconstructed value of the first adjacent signalcomponent sampling point above the current block, the reconstructedvalue of the second adjacent signal component sampling point above thecurrent block, and the reconstructed value of the second componentsampling point of the current block is only calculating the predictedvalue of the first component sampling point of the current block basedon the reconstructed value of the first adjacent signal componentsampling point above the current block, the reconstructed value of thesecond adjacent signal component sampling point above the current block,and the reconstructed value of the second component sampling point ofthe current block, that is, sampling points on the left side and on thelower left of the current block are not used in a process of calculatingthe predicted value of the first component sampling point of the currentblock.

As shown in FIG. 5, the LML mode is a prediction mode for calculating apredicted value of a first component sampling point of a current blockbased on a reconstructed value of a first adjacent signal componentsampling point on the left side of the current block, a reconstructedvalue of a second adjacent signal component sampling point on the leftside of the current block, and a reconstructed value of a secondcomponent sampling point of the current block.

In the embodiment of the present invention, the calculating thepredicted value of the first component sampling point of the currentblock based on the reconstructed value of the first adjacent signalcomponent sampling point on the left side of the current block, thereconstructed value of the second adjacent signal component samplingpoint on the left side of the current block, and the reconstructed valueof the second component sampling point of the current block is onlycalculating the predicted value of the first component sampling point ofthe current block based on the reconstructed value of the first adjacentsignal component sampling point on the left side of the current block,the reconstructed value of the second adjacent signal component samplingpoint on the left side of the current block, and the reconstructed valueof the second component sampling point of the current block, that is,sampling points right above and on the upper right of the current blockare not used in a process of calculating the predicted value of thefirst component sampling point of the current block.

In the following, with reference to FIG. 4, a prediction method for asignal component sampling point of an image block provided in anembodiment of the present invention is described as follows:calculating, based on a correlation model, a predicted value of a firstsignal component sampling point of a current block according to areconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point above the current block and a reconstructed value of asecond adjacent signal component sampling point above the current block.

As described above, in the embodiment of the present invention, a firstsignal component may be a chrominance component, and a second signalcomponent may be a luminance component. In the following, thechrominance component and the luminance component are used as an examplefor description. In the embodiment of the present invention, thecorrelation model may be a linear model, or may be a quadraticpolynomial model or another correlation model.

In the embodiment of the present invention, the term “above” in “abovethe current block” may be right above, or upper left, or upper right, ora combination of right above, upper left and upper right.

It may be understood that, adjacent signal component sampling pointsabove the current block may be all adjacent sampling points above thecurrent block, or a part of adjacent sampling points above the currentblock, for example, a part of sampling points right above and a part ofsampling points on the upper left of the current block are selected.

In the embodiment of the present invention, a size of a chrominancecomponent image of the current block is nS, a value of an adjacentchrominance component sampling point above the current block isRec_(c)[x, y], a reconstructed value of a luminance component samplingpoint of the current block is Rec_(L)[x, y] and a reconstructed value ofan adjacent luminance component sampling point above the current blockis Rec_(L)[x, y], where values of [x, y] in the two Rec_(L)[x, y] aredifferent. Output of the embodiment of the present invention is apredicted value Pred_(c)[x, y] of a chrominance component samplingpoint.

The foregoing values of the sampling points are obtained throughreconstruction in a decoding operation before this process. Because apatent technology is described by using a square block as an example inthe present invention, that the size of the chrominance component imageof the current block is nS indicates that the chrominance componentimage of the current block includes nS×nS sampling points.

This procedure includes the following steps:

S401: Perform a re-sampling operation on a reconstructed value of aluminance component sampling point of a current block and areconstructed value of an adjacent luminance component sampling pointoutside the current block, to obtain a reconstructed value Rec_(L)′[x,y]of a luminance component sampling point at a position of a chrominancecomponent sampling point of the current block, where the reconstructedvalue Rec_(L)′[x,y] is obtained after re-sampling, [x,y] indicatescoordinates of the chrominance component sampling point, and a samplingpoint in an upper left corner of the current block may be selected as anorigin of the coordinates. Definitely, if a reconstructed value of aluminance component sampling point exists at the position of thechrominance component sampling point of the current block, there-sampling operation is not required.

A re-sampling method is related to a sampling format of a video imagesignal. A purpose of re-sampling is to obtain a sampling value of aluminance component at the position of the chrominance componentsampling point of the current block. As shown in FIG. 4, for are-sampling manner used for the YUV4:2:0 format, a calculation method isas follows:Rec_(L) ′[x,y]=(Rec_(L)[2x,2y]+Rec_(L)[2x,2y+1])>>1  (2.3)

where (x, y) ε {(x, y)|x=0, . . . , 2*nS−1; y=−1}∪{(x, y)|x, y=0, . . ., nS−1}.

{(x, y)|x=0, . . . , 2*nS−1; y=−1} indicates an adjacent chrominancecomponent sampling point above the current block, {(x, y)|x, y=0, . . ., nS−1} indicates the chrominance component sampling point of thecurrent block, and Rec_(L)′[x,y] indicates a luminance componentsampling value at the position of the chrominance component samplingpoint of the current block, where the luminance component sampling valueis obtained after re-sampling.

In addition to the foregoing re-sampling method, another re-samplingmethod may also be adopted.

The foregoing adjacent chrominance component sampling point {(x, y)|x=0,. . . , 2*nS−1; y=−1} above the current block forms a template for theLMA mode. Reconstructed values of luminance components and reconstructedvalues of chrominance components of all sampling points in the templateare used for calculating parameters α and β in a linear model.

S402: Calculate the parameters α and β in the linear model.

A linear regression technique is used to calculate the parameters α andβ in the linear model. Formulas (2.4) and (2.5) show an implementationmethod.

$\begin{matrix}{\alpha = \frac{{I*{LC}} - {C*L}}{{I*{LL}} - L^{2}}} & (2.4) \\{\beta = \frac{C - {\alpha*L}}{I}} & (2.5)\end{matrix}$

where I indicates the number of sampling points in the template, Lindicates a sum of reconstructed values of all luminance componentsampling points in the template, C indicates a sum of reconstructedvalues of all chrominance component sampling points in the template, LLindicates a quadratic sum of the reconstructed values of all theluminance component sampling points in the template, and LC indicates asum of products of the reconstructed values of all the luminancecomponent sampling points and the reconstructed values of all thechrominance component sampling points in the template. L, C, LL, and LCmay be obtained through calculation by using Formulas (2.6), (2.7),(2.8), and (2.9).

$\begin{matrix}{L = {\sum\limits_{x = 0}^{{2*{nS}} - 1}{{Rec}_{L}^{\prime}\left( {x,{- 1}} \right\rbrack}}} & (2.6) \\{C = {\sum\limits_{x = 0}^{{2*{nS}} - 1}{{Rec}_{C}\left( {x,{- 1}} \right\rbrack}}} & (2.7) \\{{LL} = {\sum\limits_{x = 0}^{{2*{nS}} - 1}{{Rec}_{L}^{\prime}\left( {x,{- 1}} \right\rbrack}^{2}}} & (2.8) \\{{LC} = {\sum\limits_{x = 0}^{{2*{nS}} - 1}{{{Rec}_{L}^{\prime}\left\lbrack {x,{- 1}} \right\rbrack}*{{Rec}_{C}\left\lbrack {x,{- 1}} \right\rbrack}}}} & (2.9)\end{matrix}$

S403: Calculate a predicted value Pre_(C)[x,y] of the chrominancecomponent sampling point of the current block.

By substituting the parameters α and β obtained through calculation intothe linear model, the predicted value Pred_(C)[x, y] of the chrominancecomponent sampling point of the current block can be obtained throughcalculation based on the luminance component sampling value Rec_(L)′[x,y] at the position of the chrominance component sampling point of thecurrent block, where the luminance component sampling value Rec_(L)′[x,y] is obtained after re-sampling. An implementation manner is shown inFormula (2.10).Pred_(C) [x,y]=α*Rec_(L) ′[x,y]+β  (2.10)

where x,y=0, . . . , nS−1

In the following, with reference to FIG. 5, a prediction method for asignal component sampling point of an image block provided in anembodiment of the present invention is described as follows:calculating, based on a correlation model, a predicted value of a firstsignal component sampling point of a current block according to areconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point on the left side of the current block and a reconstructedvalue of a second adjacent signal component sampling point on the leftside of the current block.

As described above, in the embodiment of the present invention, a firstsignal component may be a chrominance component, and a second signalcomponent may be a luminance component. In the following, thechrominance component and the luminance component are used as an examplefor description. In the embodiment of the present invention, thecorrelation model may be a linear model, or may be a quadraticpolynomial model or another correlation model.

In the embodiment of the present invention, the term “left side” in “onthe left side of the current block” may be left, or upper left, or lowerleft, or a combination of left, upper left and lower left.

It may be understood that, adjacent signal component sampling points onthe left side of the current block may be all adjacent sampling pointson the left side of the current block, or a part of adjacent samplingpoints on the left side of the current block, for example, a part ofsampling points on the left of and a part of sampling points on theupper left of the current block are selected.

In the embodiment of the present invention, a size of a chrominancecomponent image of the current block is nS, a value of an adjacentchrominance component sampling point on the left side of the currentblock is Rec_(C)[x,y], a reconstructed value of a luminance componentsampling point of the current block is Rec_(L)[x, y], and areconstructed value of an adjacent luminance component sampling point onthe left side of the current block is Rec_(L)[x, y], where values of[x,y] in the two Rec_(L)[x, y] are different. Output of the embodimentof the present invention is a predicted value Pred_(C)[x, y] of achrominance component sampling point.

The foregoing values of the sampling points are obtained throughreconstruction in a decoding operation before this process. Because apatent technology is described by using a square block as an example inthe present invention, that the size of the chrominance component imageof the current block is nS indicates that the chrominance componentimage of the current block includes nS×nS sampling points.

This procedure includes the following steps:

S501: Perform a re-sampling operation on a reconstructed value of aluminance component sampling point of a current block and areconstructed value of an adjacent luminance component sampling pointoutside the current block, to obtain a luminance component samplingvalue Rec_(L)′[x,y] at a position of a chrominance component samplingpoint of the current block, where the luminance component sampling valueRec_(L)′[x,y] is obtained after re-sampling, [x,y] indicates coordinatesof the chrominance component sampling point, and a sampling point in anupper left corner of the current block may be selected as an origin ofthe coordinates. Definitely, if a reconstructed value of a luminancecomponent sampling point exists at the position of the chrominancecomponent sampling point of the current block, the re-sampling operationis not required.

A re-sampling method is related to a sampling format of a video imagesignal. A purpose of re-sampling is to obtain a reconstructed value of aluminance component sampling point at the position of the chrominancecomponent sampling point of the current block. As shown in FIG. 5, for are-sampling manner used for the YUV4:2:0 format, a calculation method isas follows:Rec_(L) ′[x,y]=(Rec_(L)[2x,2y]+Rec_(L)[2x,2y+1])>>1  (2.11)

where (x, y) ε {(x, y)|x=−1; y=0, . . . , 2*nS−1}∪{(x, y)|x, y=0, . . ., nS−1}.

{(x,y)|x=−1; y=0, . . . , 2*nS−1} indicates an adjacent chrominancecomponent sampling point on the left side of the current block, {(x,y)|x, y=0, . . . , nS−1} indicates the chrominance component samplingpoint of the current block, and Rec_(L)′[x,y] indicates the luminancecomponent sampling value at the position of the chrominance componentsampling point of the current block, where the luminance componentsampling value is obtained after re-sampling.

In addition to the foregoing re-sampling method, another re-samplingmethod may also be adopted.

The foregoing adjacent chrominance component sampling point {(x,y)|x=−1; y=0, . . . , 2*nS−1} on the left side of the current blockforms a template for the LML mode. Reconstructed values of luminancecomponents and reconstructed values of chrominance components of allsampling points in the template are used for calculating parameters αand β in a linear model.

S502: Calculate the parameters α and β in the linear model.

A linear regression technique is used to calculate the parameters α andβ in the linear model. Formulas (2.4) and (2.5) show an implementationmethod.

$\begin{matrix}{\alpha = \frac{{I*{LC}} - {C*L}}{{I*{LL}} - L^{2}}} & (2.4) \\{\beta = \frac{C - {\alpha*L}}{I}} & (2.5)\end{matrix}$

where I indicates the number of sampling points in the template, Lindicates a sum of reconstructed values of all luminance componentsampling points in the template, C indicates a sum of reconstructedvalues of all chrominance component sampling points in the template, LLindicates a quadratic sum of the reconstructed values of all theluminance component sampling points in the template, and LC indicates asum of products of the reconstructed values of all the luminancecomponent sampling points and the reconstructed values of all thechrominance component sampling points in the template. L, C, LL, and LCmay be obtained through calculation by using Formulas (2.12), (2.13),(2.14), and (2.15).

$\begin{matrix}{L = {\sum\limits_{y = 0}^{{2*{nS}} - 1}{{Rec}_{L}^{\prime}\left( {{- 1},y} \right\rbrack}}} & (2.12) \\{C = {\sum\limits_{y = 0}^{{2*{nS}} - 1}{{Rec}_{C}\left( {{- 1},y} \right\rbrack}}} & (2.13) \\{{LL} = {\sum\limits_{y = 0}^{{2*{nS}} - 1}{{Rec}_{L}^{\prime}\left( {{- 1},y} \right\rbrack}^{2}}} & (2.14) \\{{LC} = {\sum\limits_{y = 0}^{{2*{nS}} - 1}{{{Rec}_{L}^{\prime}\left\lbrack {{- 1},y} \right\rbrack}*{{Rec}_{C}\left\lbrack {{- 1},y} \right\rbrack}}}} & (2.15)\end{matrix}$

S503: Calculate a predicted value Pre_(C)[x,y] of the chrominancecomponent sampling point of the current block.

By substituting the parameters α and β obtained through calculation intothe linear model, the predicted value Pre_(C)[x, y] of the chrominancecomponent sampling point of the current block can be obtained throughcalculation based on the luminance component sampling value Rec_(L)′[x,y] at the position of the chrominance component sampling point of thecurrent block, where the luminance component sampling value Rec_(L)′[x,y] is obtained after re-sampling. An implementation manner is shown inFormula (2.10).Pred_(C) [x,y]=α*Rec_(L) ′[x,y]+β  (2.10)

where x,y=0, . . . , nS−1.

In the following, with reference to FIG. 6, an intra-frame decodingmethod for a signal component sampling point of an image block providedin an embodiment of the present invention is described.

S601: Obtain, from a video code stream, prediction mode information of afirst signal component of a current block.

S602: Determine a prediction mode of the first signal component of thecurrent block from a prediction mode set of the first signal componentof the current block according to the prediction mode information of thefirst signal component of the current block, where the prediction modeset of the first signal component of the current block includes at leastone of an LMA mode and an LML mode.

As described above, in the embodiment of the present invention, thefirst signal component may be a chrominance component, and a secondsignal component may be a luminance component. In the following, thechrominance component and the luminance component are used as an examplefor description.

In the embodiment of the present invention, the chrominance component ofthe current block may have its own independent chrominance predictionmode, or may share a same chrominance prediction mode with a chrominancecomponent of an adjacent image block. For example, in an existing HEVCencoding and decoding solution, each predicting unit has an independentprediction mode, and one predicting unit may include one or moretransform units. In an encoding and decoding process of a chrominancecomponent, a prediction operation is performed for the current blockbased on the transform unit. If one predicting unit includes only onetransform unit, the transform unit has its own independent predictionmode; and if one predicting unit includes a plurality of transformunits, the plurality of transform units uses a same prediction mode.

A decoding end may adopt an adaptive arithmetic entropy decoding method,variable length decoding, fixed length decoding or another entropydecoding method to obtain, from a code stream, prediction modeinformation of a chrominance component, where the prediction modeinformation is expressed by a code word, and then determine a predictionmode of a chrominance component of a current predicting unit accordingto correspondence between a code word and a prediction mode, so as todetermine a prediction mode of a chrominance component of a transformunit in the predicting unit, that is, the current block. Specifically,which entropy decoding method to be adopted depends on a code worddesigning method of an intra-frame prediction mode for chrominance. Acode table shown in Table 1 shows correspondence between an availablecode word and a prediction mode of a chrominance component.

TABLE 1 Code table of a prediction mode of a chrominance componentPrediction Mode of Code Word Chrominance Component 0 DM mode 101 LM mode1001 LMA mode 1000 LML mode 110 Planar mode 1110 Vertical mode 11110Horizontal mode 11111 DC mode

A code word of an original prediction mode of the chrominance componentin the HEVC solution is a Truncated Unary (TU) code. In this embodiment,a code word 10 of the LM mode is extended, and in addition, suffix codewords 1, 01, and 10 are added to distinguish the LM mode, a newly addedLMA mode, and an LML mode, so as to obtain the code table shown inTable 1. Obviously, other code words may also be selected for the LMAmode and the LML mode to form a new code table. In addition, a single TUcode, a Huffman code, a fixed length code or another code word, or acombined code word with different code words may also be adopted tospecify a corresponding code word for all prediction modes of thechrominance component, so as to form a new code table.

For the code table shown in Table 1, it may be considered that theprediction mode set of the first signal component of the current blockincludes: the DM mode, the LM mode, the LMA mode, the LML mode, theplanar mode, the vertical mode, the horizontal mode, and the DC mode.

S603: Obtain a predicted value of a first signal component samplingpoint of the current block according to the prediction mode of the firstsignal component of the current block.

In the embodiment of the present invention, if the prediction mode ofthe first signal component of the current block that is determined fromthe prediction mode set of the first signal component of the currentblock according to the prediction mode information of the first signalcomponent of the current block is the LMA mode, the obtaining apredicted value of a first signal component sampling point of thecurrent block according to the prediction mode of the first signalcomponent of the current block includes: calculating, based on acorrelation model, the predicted value of the first signal componentsampling point of the current block according to a reconstructed valueof a second signal component sampling point of the current block and aparameter of the correlation model, where the parameter of thecorrelation model is obtained through calculation according to areconstructed value of a first adjacent signal component sampling pointabove the current block and a reconstructed value of a second adjacentsignal component sampling point above the current block.

If the prediction mode of the first signal component of the currentblock that is determined from the prediction mode set of the firstsignal component of the current block according to the prediction modeinformation of the first signal component of the current block is theLML mode, the obtaining a predicted value of a first signal componentsampling point of the current block according to the prediction mode ofthe first signal component of the current block includes: calculating,based on a correlation model, the predicted value of the first signalcomponent sampling point of the current block according to areconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point on the left side of the current block and a reconstructedvalue of a second adjacent signal component sampling point on the leftside of the current block.

A specific prediction method has been described in detail in theembodiments shown in FIG. 4 and FIG. 5, and is not described hereinagain.

S604: Obtain a reconstructed value of the first signal componentsampling point of the current block according to the predicted value ofthe first signal component sampling point of the current block.

A reconstructed value of a chrominance component sampling point of thecurrent block is calculated based on an obtained predicted value of thechrominance component sampling point of the current block and a residualvalue of the chrominance component sampling point of the current block,where the residual value is obtained through reconstruction. Theresidual value of the chrominance component sampling point of thecurrent block may be obtained based on residual information of thechrominance component sampling point of the current block, where theresidual information is obtained from a video code stream. Specifically,the H.264/AVC standard or a method in the existing HEVC solution may beadopted to reconstruct the residual value of the chrominance componentsampling point of the current block, which is not described hereinagain.

In some implementation manners, another code table may be adopted inS602, and a code table shown in Table 2 shows correspondence between anavailable code word and a prediction mode of a chrominance component.

TABLE 2 Code table of a prediction mode of a chrominance componentPrediction Mode of Code Word Chrominance Component 0 DM mode 10 LM mode110 LMA mode 111 LML mode

Code words of original six prediction modes of the chrominance componentin the HEVC solution are TU codes. In this embodiment, four existingHEVC prediction modes are removed, and TU codes are used to design codewords for the LMA, LML and other remaining modes. Obviously, the codetable may also be redesigned by removing one or more other existing HEVCprediction modes, or adding a new suitable prediction mode. A new codetable may adopt a single TU code, a Huffman code, a fixed length code oranother code word, or a combined code word with different code words tospecify a corresponding code word for all optional prediction modes ofthe chrominance component.

For the code table shown in Table 1, it may be considered that theprediction mode set of the first signal component of the current blockincludes: the DM mode, the LM mode, the LMA mode, and the LML mode.

According to the technical solution provided in the embodiment of thepresent invention, by using a technical means of providing a predictionmode set including an LMA mode and an LML mode for a chrominancecomponent, the accuracy of intra-frame prediction of a current block isimproved.

In the following, with reference to FIG. 7, an intra-frame decodingmethod for a signal component sampling point of an image block providedin an embodiment of the present invention is described.

S701: Obtain, from a video code stream, prediction mode information of afirst signal component of a current block.

S702: Determine a prediction mode of the first signal component of thecurrent block from a prediction mode set of the first signal componentof the current block according to the prediction mode information of thefirst signal component of the current block, where the prediction modeset of the first signal component includes a prediction mode based on acorrelation model, and the prediction mode based on the correlationmodel is determined depending on a prediction mode of a second signalcomponent of the current block.

In the embodiment of the present invention, the prediction mode based onthe correlation model includes a prediction mode for calculating apredicted value of a first signal component sampling point of thecurrent block by using the correlation model according to areconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model; and theprediction mode based on the correlation model may include any one ofthe following prediction modes: an LM mode, an LMA mode, and an LMLmode.

In the embodiment of the present invention, a parameter of thecorrelation model of the LMA mode is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point above the current block and a reconstructed value of asecond adjacent signal component sampling point above the current block;a parameter of the correlation model of the LML mode is obtained throughcalculation according to a reconstructed value of a first adjacentsignal component sampling point on the left side of the current blockand a reconstructed value of a second adjacent signal component samplingpoint on the left side of the current block; and a parameter of thecorrelation model of the LM mode is obtained through calculationaccording to the reconstructed values of the first adjacent signalcomponent sampling points above and on the left side of the currentblock and the reconstructed values of the second adjacent signalcomponent sampling points above and on the left side of the currentblock.

As described above, in the embodiment of the present invention, thefirst signal component may be a chrominance component, and the secondsignal component may be a luminance component. In the following, thechrominance component and the luminance component are used as an examplefor description.

In the embodiment of the present invention, the chrominance component ofthe current block may have its own independent chrominance predictionmode, or may share a same chrominance prediction mode with a chrominancecomponent of an adjacent image block. For example, in an existing HEVCencoding and decoding solution, each predicting unit has an independentprediction mode, and one predicting unit may include one or moretransform units. In a frame encoding and decoding process of achrominance component, a prediction operation is performed for thecurrent block based on the transform unit. If one predicting unitincludes only one transform unit, the transform unit has its ownindependent prediction mode; and if one predicting unit includes aplurality of transform units, the plurality of transform units uses asame prediction mode.

A decoding end may adopt an adaptive arithmetic entropy decoding method,variable length decoding, fixed length decoding or another entropydecoding method to obtain, from a code stream, prediction modeinformation of a chrominance component, where the prediction modeinformation is expressed by a code word, and then determine a predictionmode of a chrominance component of a current predicting unit accordingto correspondence between a code word and a prediction mode, so as todetermine a prediction mode of a chrominance component of a transformunit in the predicting unit, that is, the current block. Specifically,which entropy decoding method to be adopted depends on a code worddesigning method of an intra-frame prediction mode for chrominance. Acode table shown in Table 3 shows correspondence between an availablecode word and a prediction mode of a chrominance component.

TABLE 3 Code table of a prediction mode of a chrominance componentPrediction Mode of Code Word Chrominance Component 0 DM mode 101 Firstmode 100 Second mode 110 Planar mode 1110 Vertical mode 11110 Horizontalmode 11111 DC mode

In the embodiment of the present invention, the first mode or the secondmode is a prediction mode based on a correlation model, and may be oneof the LM mode, the LML mode, and the LMA mode. When it is determinedthat the prediction mode of the chrominance component is the first modeor the second mode, a prediction mode specifically indicated by thefirst mode or the second mode needs to be obtained based on a presetmapping table according to a prediction mode of a luminance component ofthe current block. The foregoing mapping table is used at both anencoding end and a decoding end. For example, the prediction modesspecifically indicated by the first mode and the second mode may bedetermined based on a mapping shown in Table 4 according to theprediction mode of the luminance component. Obviously, the mapping has aplurality of combinations, and is not limited to Table 4.

TABLE 4 Mapping between the prediction mode of the luminance componentand the first mode and the second mode Infra-frame Prediction Mode forLuminance First Mode Second Mode Vertical mode LM mode LMA modeHorizontal mode LM mode LML mode DC mode LM mode LML mode Anotherintra-frame LML mode LMA mode prediction mode

A code word of an original prediction mode of the chrominance componentin the HEVC solution is a TU code. In this embodiment, a code word 10 ofthe LM mode is extended, and in addition, suffix code words 1 and 0 areadded to distinguish the first mode from the second mode, so as toobtain the code table shown in Table 3. Obviously, other code words maybe selected for the first mode and the second mode to form a new codetable, and a single TU code, a Huffman code, a fixed length code oranother code word, or a combined code word with different code words mayalso be adopted to specify a corresponding code word for all optionalprediction modes of the chrominance component, so as to form a new codetable.

For convenience of understanding, in the embodiment of the presentinvention, possible methods of determining the prediction mode of thechrominance component of the current block are briefly described byusing examples. For example, in some implementation manners, if it isdetermined, according to the prediction mode information of thechrominance component, that the prediction mode of the chrominancecomponent of the current block is a prediction mode based on acorrelation model, that is, the first mode or the second mode shown inTable 3, the prediction mode of the chrominance component of the currentblock is determined based on Table 4 according to the prediction mode ofthe luminance component of the current block. For another example, insome implementation manners, the first mode and the second mode shown inTable 3 may also be determined based on Table 4 according to theprediction mode of the luminance component of the current block, and inthis case, the prediction mode of the chrominance component of thecurrent block may be determined directly according to the predictionmode information of the chrominance component.

For the code table shown in Table 3, it may be considered that theprediction mode set of the first signal component of the current blockincludes at least one prediction mode of the DM mode, the planar mode,the vertical mode, the horizontal mode, the DC mode, and the predictionmode based on the correlation model.

S703: Obtain a predicted value of a first signal component samplingpoint of the current block according to the prediction mode of the firstsignal component of the current block.

In the embodiment of the present invention, if the prediction mode ofthe first signal component of the current block that is determined fromthe prediction mode set of the first signal component of the currentblock according to the prediction mode information of the first signalcomponent of the current block is the LMA mode, the obtaining apredicted value of a first signal component sampling point of thecurrent block according to the prediction mode of the first signalcomponent of the current block includes: calculating, based on thecorrelation model, the predicted value of the first signal componentsampling point of the current block according to the reconstructed valueof the second signal component sampling point of the current block andthe parameter of the correlation model, where the parameter of thecorrelation model is obtained through calculation according to thereconstructed value of the first adjacent signal component samplingpoint above the current block and the reconstructed value of the secondadjacent signal component sampling point above the current block.

If the prediction mode of the first signal component of the currentblock that is determined from the prediction mode set of the firstsignal component of the current block according to the prediction modeinformation of the first signal component of the current block is theLML mode, the obtaining a predicted value of a first signal componentsampling point of the current block according to the prediction mode ofthe first signal component of the current block includes: calculating,based on the correlation model, the predicted value of the first signalcomponent sampling point of the current block according to thereconstructed value of the second signal component sampling point of thecurrent block and the parameter of the correlation model, where theparameter of the correlation model is obtained through calculationaccording to the reconstructed value of the first adjacent signalcomponent sampling point on the left side of the current block and thereconstructed value of the second adjacent signal component samplingpoint on the left side of the current block.

A specific prediction method has been described in detail in theembodiments shown in FIG. 4 and FIG. 5, and is not described hereinagain.

S704: Obtain a reconstructed value of the first signal componentsampling point of the current block according to the predicted value ofthe first signal component sampling point of the current block.

A reconstructed value of a chrominance component sampling point of thecurrent block is calculated based on an obtained predicted value of thechrominance component sampling point of the current block and a residualvalue of the chrominance component sampling point of the current block,where the residual value is obtained through reconstruction. Theresidual value of the chrominance component sampling point of thecurrent block may be obtained based on residual information of thechrominance component sampling point of the current block, where theresidual information is obtained from a video code stream. Specifically,the H.264/AVC standard or a method in the existing HEVC solution may beadopted to reconstruct the residual value of the chrominance componentsampling point of the current block, which is not described hereinagain.

In some implementation manners, another code table may be adopted inS702, and a code table shown in Table 5 shows correspondence between anavailable code word and a prediction mode of a chrominance component.

TABLE 5 Code table of a prediction mode of a chrominance componentPrediction Mode of Code Word Chrominance Component 0 DM mode 10 Firstmode 110 Planar mode 1110 Vertical mode 11110 Horizontal mode 11111 DCmode

In the embodiment of the present invention, the first mode is aprediction mode based on a correlation model, and may be one of the LMmode, the LML mode, and the LMA mode. When it is determined that theprediction mode of the chrominance component is the first mode, aprediction mode specifically indicated by the first mode needs to bedetermined based on a preset mapping table according to a predictionmode of a luminance component of the current predicting unit. Theforegoing mapping table is used at both an encoding end and a decodingend. Table 6 shows a mapping between an available prediction mode of theluminance component and the first mode. Obviously, the mapping has aplurality of combinations, and is not limited to Table 6.

TABLE 6 Mapping between the prediction mode of the luminance componentand the first mode Prediction Mode of Luminance Component First ModeVertical mode LMA mode Horizontal mode LML mode DC mode LML mode Anotherintra-frame LM mode prediction mode

A code word of an original prediction mode of the chrominance componentin the HEVC solution is a TU code. In this embodiment, code words of allthe optional prediction modes of the chrominance component still use TUcodes. Obviously, a single Huffman code, a fixed length code or anothercode word, or a combined code word with different code words may also beadopted to specify a corresponding code word for all the optionalprediction modes of chrominance component, so as to form a new codetable.

For convenience of understanding, in the embodiment of the presentinvention, possible methods of determining the prediction mode arebriefly described by using examples. For example, in some implementationmanners, if it is determined, according to the prediction modeinformation of the chrominance component, that the prediction mode ofthe chrominance component of the current block is a prediction modebased on a correlation model, that is, the first mode shown in Table 5,the prediction mode of the chrominance component of the current block isdetermined based on Table 6 according to the prediction mode of theluminance component of the current block. For another example, in someimplementation manners, the first mode shown in Table 5 may bedetermined based on Table 6 according to the prediction mode of theluminance component of the current block, and in this case, theprediction mode of the chrominance component of the current block may bedetermined directly according to the prediction mode information of thechrominance component.

For the code table shown in Table 5, it may be considered that theprediction mode set of the first signal component of the current blockincludes at least one prediction mode of the DM mode, the planar mode,the vertical mode, the horizontal mode, the DC mode, and the predictionmode based on the correlation model.

According to the technical solution provided in the embodiment of thepresent invention, by using a technical means of providing a predictionmode set including an LMA mode and an LML mode for a chrominancecomponent, the accuracy of intra-frame prediction of a current block isimproved.

With the technical solution provided in the embodiment of the presentinvention, the accuracy of intra-frame prediction of a current block isimproved, and beneficial effects of the embodiment of the presentinvention are described in detail from the following two aspects.

The first aspect is a subjective aspect. FIG. 8 shows a V component of areconstructed image obtained by using the solution in the embodiment ofthe present invention, and FIG. 9 shows a V component of a reconstructedimage obtained by using an existing HEVC solution (that is, predictionmodes of a chrominance component include only a DM mode, an LM mode, ahorizontal mode, a vertical mode, a planar mode, and a DC mode). It canbe seen by comparing FIG. 8 and FIG. 9 that the reconstructed imageshown in FIG. 8 is sharper, and has clearer details. This is because twooptional prediction modes of the chrominance component that are newlyadded in the embodiment of the present invention enable intra-frameprediction of the chrominance component to be more accurate, so that aprediction residual is smaller. Accordingly, distortion caused byquantization of the prediction residual is not obvious, therebyobtaining a better reconstructed image.

In the second aspect, comparison that uses a method for objectivelyevaluating Blue-ray Disc Bitrate (BD-Bitrate) shows that the embodimentof the present invention has better rate distortion performance.Specific data is shown in Table 7. Values shown in Table 7 indicate apercentage of a bit rate saved by the embodiment of the presentinvention, compared with the existing HEVC solution. If the percentageis negative, the bit rate is saved; and if the percentage is positive,the bit rate is increased.

TABLE 7 All Intra HE All Intra LC Y U V Y U V Class A −0.2% −9.1%  −9.9%−0.1% −9.3%  −10.1%  Class B −0.1% −2.7%  −2.2%   0.0% −2.8%  −2.2%Class C −0.2% −2.3%  −2.9% −0.1% −2.2%  −2.7% Class D −0.1% −2.0%  −2.2%−0.1% −2.0%  −2.2% Class E −0.1% −1.5%  −1.8%   0.0% −1.9%  −1.8% ClassF −0.3% −2.6%  −2.9% −0.2% −2.2%  −2.6% Overall −0.2% −3.4%  −3.6% −0.1%−3.4%  −3.6% −0.2% −3.4%  −3.6% −0.1% −3.4%  −3.5% Enc Time 105% 107%[%] Dec Time 100% 100% [%]

FIG. 10 is a rate-distortion diagram showing comparison of results ofencoding a sequence SteamLocomotive by using the embodiment of thepresent invention and the existing HEVC solution HEVC Test Model (HM)4.0. It can be seen that, with the method provided in the presentinvention, encoding performance is definitely enhanced, and subjectivequality is improved.

As shown in FIG. 11, an embodiment of the present invention provides aprediction apparatus for a signal component sampling point of an imageblock, which includes: a first parameter unit 1101 configured to obtaina parameter of a correlation model through calculation according to areconstructed value of a first adjacent signal component sampling pointabove a current block and a reconstructed value of a second adjacentsignal component sampling point above the current block; and a firstpredicting unit 1102 configured to calculate, based on the correlationmodel, a predicted value of a first signal component sampling point ofthe current block according to a reconstructed value of a second signalcomponent sampling point of the current block and the parameter of thecorrelation model.

The apparatus provided in the embodiment of the present invention isconfigured to implement the method shown in FIG. 4, which is notdescribed herein again.

As shown in FIG. 12, an embodiment of the present invention provides aprediction apparatus for a signal component sampling point of an imageblock, which includes: a second parameter unit 1201 configured to obtaina parameter of a correlation model through calculation according to areconstructed value of a first adjacent signal component sampling pointon the left side of a current block and a reconstructed value of asecond adjacent signal component sampling point on the left side of thecurrent block; and a second predicting unit 1202 configured tocalculate, based on the correlation model, a predicted value of a firstsignal component sampling point of the current block according to areconstructed value of a second signal component sampling point of thecurrent block and the parameter of the correlation model.

The apparatus provided in the embodiment of the present invention isconfigured to implement the method shown in FIG. 5, which is notdescribed herein again.

As shown in FIG. 13, an embodiment of the present invention provides anintra-frame decoding apparatus for a signal component sampling point ofan image block, which includes: a first obtaining unit 1301 configuredto obtain, from a video code stream, prediction mode information of afirst signal component of a current block; a first determining unit 1302configured to determine a prediction mode of the first signal componentof the current block from a prediction mode set of the first signalcomponent of the current block according to the prediction modeinformation of the first signal component of the current block, wherethe prediction mode set of the first signal component of the currentblock includes at least one of an LMA mode and an LML mode; a thirdpredicting unit 1303 configured to obtain a predicted value of a firstsignal component sampling point of the current block according to theprediction mode of the first signal component of the current block; anda first calculating unit 1304 configured to obtain a reconstructed valueof the first signal component sampling point of the current blockaccording to the predicted value of the first signal component samplingpoint of the current block.

The apparatus provided in the embodiment of the present invention isconfigured to implement the method shown in FIG. 6, which is notdescribed herein again.

According to the apparatus provided in the embodiment of the presentinvention, by using a technical means of providing a prediction mode setincluding an LMA mode and an LML mode for a chrominance component, theaccuracy of intra-frame prediction of a current block is improved.

As shown in FIG. 14, an embodiment of the present invention provides anintra-frame decoding apparatus for a signal component sampling point ofan image block, which includes: a second obtaining unit 1401 configuredto obtain, from a video code stream, prediction mode information of afirst signal component of a current block; a second determining unit1402 configured to determine a prediction mode of the first signalcomponent of the current block from a prediction mode set of the firstsignal component of the current block according to the prediction modeinformation of the first signal component of the current block, wherethe prediction mode set of the first signal component includes aprediction mode based on a correlation model, and the prediction modebased on the correlation model is determined depending on a predictionmode of a second signal component of the current block; a fourthpredicting unit 1403 configured to obtain a predicted value of a firstsignal component sampling point of the current block according to theprediction mode of the first signal component of the current block; anda second calculating unit 1404 configured to obtain a reconstructedvalue of the first signal component sampling point of the current blockaccording to the predicted value of the first signal component samplingpoint of the current block.

The apparatus provided in the embodiment of the present invention isconfigured to implement the method shown in FIG. 7, which is notdescribed herein again.

According to the apparatus provided in the embodiment of the presentinvention, by using a technical means of providing a prediction mode setincluding an LMA mode and an LML mode for a chrominance component, theaccuracy of intra-frame prediction of a current block is improved.

The technology provided in the embodiments of the present invention maybe applied to the field of digital signal processing and may beimplemented by using an encoder and a decoder. A video encoder anddecoder are widely applied to various communications devices orelectronic devices, such as a digital television, a set top box, a mediagateway, a mobile phone, a wireless apparatus, a personal digitalassistant (PDA), a handheld or portable computer, a global positioningsystem (GPS) receiver/navigator, a camera, a video player, a videocamera, a video tape recorder, a monitoring device, and a videoconference and a videophone device. Such a device includes a processor,a memory, and an interface for data transmission. A video codec may bedirectly implemented by a digital circuit or a chip, such as a digitalsignal processor (DSP), or may be implemented by software code driving aprocessor to execute a procedure in the software code.

Persons of ordinary skill in the art may understand that all or a partof the steps of the foregoing method embodiments of the presentinvention may be implemented by a program instructing relevant hardware.The foregoing program may be stored in a computer readable storagemedium. When the program is run, the steps of the foregoing methodembodiments are performed. The foregoing storage medium includes anymedium that is capable of storing program code, such as a read-onlymemory (ROM), a random-access memory (RAM), a magnetic disk, or anoptical disc.

Finally, it should be noted that the foregoing embodiments are merelyintended for describing the technical solutions of the present inventionrather than limiting the present invention. Although the presentinvention is described in detail with reference to the foregoingembodiments, persons of ordinary skill in the art should understand thatthey may still make modifications to the technical solutions describedin the foregoing embodiments or make equivalent replacements to sometechnical features thereof, as long as such modifications orreplacements do not make the essence of corresponding technicalsolutions depart from the spirit and scope of the technical solutions inthe embodiments of the present invention.

What is claimed is:
 1. A prediction method for a signal componentsampling point of an image block, comprising: calculating, based on acorrelation model, a predicted value of a first signal componentsampling point of a current block according to a reconstructed value ofa second signal component sampling point of the current block and aparameter of the correlation model, wherein the parameter of thecorrelation model is obtained through calculation according to areconstructed value of a first adjacent signal component sampling pointin a reference block and a reconstructed value of a second adjacentsignal component sampling point in the reference block, and wherein thereference block comprises one of the following blocks: an upper leftblock of the current block, an upper block of the current block and acombination block of right above block, upper left block and upper rightblock of the current block.
 2. The method according to claim 1, whereina first signal component is a chrominance component, and the secondsignal component is a luminance component.
 3. A prediction method for asignal component sampling point of an image block, comprising:calculating, based on a correlation model, a predicted value of a firstsignal component sampling point of a current block according to areconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model, wherein theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point in a reference block and a reconstructed value of asecond adjacent signal component sampling point in the reference block,and wherein the reference block comprises one of the following blocks:an upper left block of the current block, a lower left block of thecurrent block and a combination block of left block, upper left blockand lower left block of the current block.
 4. The method according toclaim 3, wherein a first signal component is a chrominance component,and the second signal component is a luminance component.
 5. Anintra-frame decoding method for a signal component sampling point of animage block, comprising: obtaining, from a video code stream, predictionmode information of a first signal component of a current block;determining a prediction mode of the first signal component of thecurrent block from a prediction mode set of the first signal componentof the current block according to the prediction mode information of thefirst signal component of the current block, wherein the prediction modeset of the first signal component of the current block comprises atleast one of a linear model above (LMA) mode and a linear model left(LML) mode, wherein the LMA mode is a prediction mode for calculating apredicted value of a first component sampling point of the current blockbased on the reconstructed value of the first adjacent signal componentsampling point above the current block, the reconstructed value of thesecond adjacent signal component sampling point above the current block,and a reconstructed value of a second component sampling point of thecurrent block, wherein the LML mode is a diction mode for calculatingthe predicted value of the first component sampling point of the currentblock based on the reconstructed value of the first adjacent signalcomponent sampling point on the left side of the current block, thereconstructed value of the second adjacent signal component samplingpoint on the left side of the current block, and the reconstructed valueof the second component sampling point of the current block, and whereina linear method (LM) mode is a prediction mode for calculating thepredicted value of the first component sampling point of the currentblock based on the reconstructed values of the first adjacent signalcomponent sampling points above and on the left side of the currentblock, the reconstructed values of the second adjacent signal componentsampling points above and on the left side of the current block, and thereconstructed value of the second component sampling point of thecurrent block; obtaining a predicted value of a first signal componentsampling point of the current block according to the prediction mode ofthe first signal component of the current block; and obtaining areconstructed value of the first signal component sampling point of thecurrent block according to the predicted value of the first signalcomponent sampling point of the current block.
 6. The method accordingto claim 5, wherein when the prediction mode of the first signalcomponent of the current block that is determined from the predictionmode set of the first signal component of the current block according tothe prediction mode information of the first signal component of thecurrent block is the LMA mode, obtaining the predicted value of thefirst signal component sampling point of the current block according tothe prediction mode of the first signal component of the current blockcomprises: calculating, based on a correlation model, the predictedvalue of the first signal component sampling point of the current blockaccording to a reconstructed value of a second signal component samplingpoint of the current block and a parameter of the correlation model,wherein the parameter of the correlation model is obtained throughcalculation according to a reconstructed value of a first adjacentsignal component sampling point above the current block and areconstructed value of a second adjacent signal component sampling pointabove the current block.
 7. The method according to claim 5, whereinwhen the prediction mode of the first signal component of the currentblock that is determined from the prediction mode set of the firstsignal component of the current block according to the prediction modeinformation of the first signal component of the current block is theLML, mode, obtaining the predicted value of the first signal componentsampling point of the current block according to the prediction mode ofthe first signal component of the current block comprises: calculating,based on a correlation model, the predicted value of the first signalcomponent sampling point of the current block according to areconstructed value of a second signal component sampling point of thecurrent block and a parameter of the correlation model, wherein theparameter of the correlation model is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point on the left side of the current block and a reconstructedvalue of a second adjacent signal component sampling point on the leftside of the current block.
 8. The method according to claim 5, whereinthe prediction mode set of the first signal component of the currentblock comprises a direct mode (DM) mode, an LM mode, the LMA mode, theLML mode, a planar mode, a vertical mode, a horizontal mode, and a DCmode.
 9. The method according to claim 5, wherein the prediction modeset of the first signal component of the current block comprises a DMmode, an LM mode, the LMA mode, and the LML mode.
 10. The methodaccording to claim 5, wherein the first signal component is achrominance component, and a second signal component is a luminancecomponent.
 11. An intra-frame decoding method for a signal componentsampling point of an age block, comprising: obtaining, from a video codestream, prediction mode information of a first signal component of acurrent block; determining a prediction mode of the first signalcomponent of the current block from a prediction mode set of the firstsignal component of the current block according to the prediction modeinformation of the first signal component of the current block, Whereinthe prediction mode set of the first signal component comprises aprediction mode based on a correlation model, and the prediction modebased on the correlation model is determined depending on a predictionmode of a second signal component of the current block; obtaining apredicted value of a first signal component sampling point of thecurrent block according to the prediction mode of the first signalcomponent of the current block; and obtaining a reconstructed value ofthe first signal component sampling point of the current block accordingto the predicted value of the first signal component sampling point ofthe current block, wherein the prediction mode based on the correlationmodel is a prediction mode for calculating the predicted value of thefirst signal component sampling point of the current block by using thecorrelation model according to a reconstructed value of a second signalcomponent sampling point of the current block and a parameter of thecorrelation model, wherein the prediction mode based on the correlationmodel is any one of the following prediction modes a linear method (LM)mode, a linear model above (LMA) mode, and a linear model left (LML)mode, wherein the LMA mode is a prediction mode for calculating apredicted value of a first component sampling point of the current blockbased on the reconstructed value of the first adjacent signal componentsampling point above the current block, the reconstructed value of thesecond adjacent signal component sampling point above the current block,and a reconstructed value of a second component sampling point of thecurrent block, wherein the LML mode is a prediction mode for calculatingthe predicted value of the first component sampling point of the currentblock based on the reconstructed value of the first adjacent signalcomponent sampling point on the left side of the current block, thereconstructed value of the second adjacent signal component samplingpoint on the left side of the current block, and the reconstructed valueof the second component sampling point of the current block, and whereinthe LM mode is a prediction mode for calculating the predicted value ofthe first component sampling point of the current block based on thereconstructed values of the first adjacent signal component samplingpoints above and on the left side of the current block, thereconstructed values of the second adjacent signal component samplingpoints above and on the left side of the current block, and thereconstructed value of the second component sampling point of thecurrent block.
 12. The method according to claim 11, wherein a parameterat the correlation model of the LMA mode is obtained through calculationaccording to a reconstructed value of a first adjacent signal componentsampling point above the current block and a reconstructed value of asecond adjacent signal component sampling point above the current block,wherein a parameter of the correlation model of the LML mode is obtainedthrough calculation according to a reconstructed value of a firstadjacent signal component sampling point on the left side of the currentblock and a reconstructed value of a second adjacent signal componentsampling point on the left side of the current block, and wherein aparameter of the correlation model of the LM mode is obtained throughcalculation according to the reconstructed values of the first adjacentsignal component sampling points above and on the left side of thecurrent block and the reconstructed values of the second adjacent signalcomponent sampling points above and on the left side of the currentblock.
 13. The method according to claim 11, wherein when the predictionmode of the first signal component of the current block that isdetermined from the prediction mode set of the first signal component ofthe current block according to the prediction mode information of thefirst signal component of the current block is the LMA mode, obtainingthe predicted value of the first signal component sampling point of thecurrent block according to the prediction mode of the first signalcomponent of the current block comprises: calculating, based on thecorrelation model, the predicted value of the first signal componentsampling point of the current block according to the reconstructed valueof the second signal component sampling point of the current block andthe parameter of the correlation model, wherein the parameter of thecorrelation model is obtained through calculation according to thereconstructed value of the first adjacent signal component samplingpoint above the current block and the reconstructed value of the secondadjacent signal component sampling point above the current block. 14.The method according to claim 11, wherein when the prediction mode ofthe first signal component of the current block that is determined fromthe prediction mode set of the first signal component of the currentblock according to the prediction mode information of the first signalcomponent of the current block is the LML mode, obtaining the predictedvalue of the first signal component sampling point of the current blockaccording to the prediction mode of the first signal component of thecurrent block comprises: calculating, based on the correlation model,the predicted value of the first signal component sampling point of thecurrent block according to the reconstructed value of the second signalcomponent sampling point of the current block and the parameter of thecorrelation model, wherein the parameter of the correlation model isobtained through calculation according to the reconstructed value of thefirst adjacent signal component sampling point on the left side of thecurrent block and the reconstructed value of the second adjacent signalcomponent sampling point on the left side of the current block.
 15. Themethod according to claim 11, wherein the prediction mode set of thefirst signal component of the current block comprises at least oneprediction mode of a direct mode (DM) mode, a planar mode, a verticalmode, a horizontal mode, a direct current (DC) mode, and the predictionmode based on the correlation model.
 16. The method according to claim11, wherein the LMA mode is a prediction mode for calculating apredicted value of a first component sampling point of the current blockbased on the reconstructed value of the first adjacent signal componentsampling point above the current block, the reconstructed value of thesecond adjacent signal component sampling point above the current block,and a reconstructed value of a second component sampling point of thecurrent block, wherein the LML mode is a prediction mode for calculatingthe predicted value of the first component sampling point of the currentblock based on the reconstructed value of the first adjacent signalcomponent sampling point on the left side of the current block, thereconstructed value of the second adjacent signal component samplingpoint on the left side of the current block, and the reconstructed valueof the second component sampling point of the current block, and whereinthe LM mode is a prediction mode for calculating the predicted value ofthe first component sampling point of the current block based on thereconstructed values of the first adjacent signal component samplingpoints above and on the left side of the current block, thereconstructed values of the second adjacent signal component samplingpoints above and on the left side of the current block, and thereconstructed value of the second component sampling point of thecurrent block.
 17. The method according to claim 11, wherein the firstsignal component is a chrominance component, and the second signalcomponent is a luminance component.